This project aims to determine if certain biological factors, namely abnormalities on the CAT Scan, low platelet MAO, or left-handedness have an etiological relationship with schizophrenia. The method involves finding schizophrenics with one of these factors and studying the relatives to see if the factor and schizophrenia segregate toghether in these pedigrees. After the collection of the CAT Scan data on the sample of 20 schizophrenics, the work on this project shifted to study the meaning of those abnormalities found. Neuropsychological testing, including the Halstead-Reitan Battery, was administered to those schizophrenics with and without CAT Scans showing enlargement of the sulci (cortical atrophy) and ventricular enlargement. A significant relationship appears to exist between performance on the Halstead-Reitan Battery and enlargement of the sulci among these young chronic schizophrenics. Sulcal enlargement was not commonly found (4 cases of 20), but may indicate a previously unrecognized organic brain impairment.